If I see my friend engaged in a potentially dangerous behavior, I would tell her honestly what I think about it because I believe that's what friends are for. If I consider someone a friend, I am not going to just sit and watch them engaging in self-destructive behavior without saying anything. However, once I say it, I no longer get emotionally invested in what they do, meaning that I would not try to persuade them to do what I think is best for them. They are an adult and it's not my place to take care of them. Caring is not the same as taking care. Caring to me is being honest about what I think and coming from a compassionate place when I do that. Taking care is trying to influence someone's choices, and while it may come from the good intention, it's an inappropriate interference in the life of an adult.

That being said, I would talk to my friend in the hope that she will listen and self-reflect on her behavior, but I would not contact her therapist. I would talk to her once and then will leave her alone and would refuse to discuss this topic again since I've already given her my opinion.